Catheters have been placed in the body of a patient and used to supply anticancer agents, nutritional formulations, or other such items into a patient's vein either temporarily or on a long-term basis. To infuse a stabilized drug solution with the use of a catheter in this fashion, it is important that infection and complications be prevented, that the catheter not break or move, and that the catheter also does not become occluded. However, when a catheter with an open tip is used, blood sometimes enters the catheter, coagulates, and the catheter becomes occluded. To prevent occlusion of catheters from such blood coagulation, the interior space of the catheter is generally filled with physiological saline including added heparin; however, this practice is problematic in that it complicates procedures when a catheter is placed in the body of a patient and represents a burden on health care providers and patients.
Consequently, a catheter including a valve able to prevent occlusion of the catheter due to coagulation of blood has been developed (e.g., see Japanese Unexamined Patent Application Publication S60-58167) by eliminating the tip opening and providing a valve which is normally closed and opens only at times such as when a drug solution is infused between the inside and the outside of the catheter or when blood is collected. Such a catheter with valve (bidirectional valve) is made from an elastic, plastic material, the tip is closed, and at the tip there is formed a linear slit. As a result, when a predetermined pressure differential develops between the inside and outside of such a catheter with valve, the slit opens, and a drug solution can be infused into a vein, or blood within a vein can be released into the catheter and collected. When a predetermined pressure differential between the inside and outside of a catheter with the valve has not developed, the slit is closed, and there is consequently no coagulation of blood within the slit.
Nonetheless, when a drug solution flows from the inside to the outside of a conventional catheter with valve described above, the slit closes with comparative ease, but a problem exists in that when blood flows from outside toward the inside of the catheter with the valve, the opposing surfaces which form the slit are subject to contact pressure, and it is difficult for the slit to open.
Therefore, it would be beneficial to have a catheter with a valve capable of providing a smooth the flow of a liquid both when a liquid flows from the inside toward the outside of the catheter, and when a liquid flows from the outside toward the inside of the catheter.